improve support for backspace

I still don't understand the entire state space here, so I'm trying to
err on the side of improving discoverability of the `ctrl-h` escape
hatch. Without requiring too wide a window to show all hotkeys on the
menu.

README.md

@@ -122,7 +122,15 @@ a say in its future direction.
   call to `assume_default_colors()` in function `main()` at the bottom of
   `src/lua.c`. If you do this, you'll likely also need to tweak other colors
   for legibility. Look for calls to `FG()`, `BG()` and `COLOR_PAIR()`.
-  ```
+
+* Backspace is known to not work in some configurations. As a workaround,
+  typing `ctrl-h` tends to work in those situations.
+
+* Keys outside the main keyboard area are mostly not supported. This includes
+  the delete key when it's set away from the main keyboard area. (Macs call
+  the backspace key “delete”; it should behave like backspace. As
+  a consequence the menu sometimes mentions keys that don't work, just to
+  encourage people to try options.)
 
 ## What's with the name?
 

src/kilo.c

@@ -674,6 +674,8 @@ static void editorMenu(void) {
     draw_menu_item("^b", "big picture");
     draw_menu_item("^f", "find");
     draw_menu_item("^/", "(un)comment line");
+    draw_menu_item("^h", "back up cursor");
+    draw_menu_item("^l", "end of line");
     attrset(A_NORMAL);
 }
 
@@ -830,7 +832,7 @@ static void editorFind() {
         mvprintw(LINES-2, 0, "Find: %s", query);
 
         int c = getch();
-        if (c == TELIVA_BACKSPACE) {
+        if (c == KEY_BACKSPACE || c == DELETE || c == CTRL_H) {
             if (qlen != 0) query[--qlen] = '\0';
             last_match = -1;
         } else if (c == ESC || c == ENTER) {
@@ -1033,7 +1035,7 @@ static void editorGo(lua_State* L) {
         mvprintw(LINES-2, 0, "Go to: %s", query);
 
         int c = getch();
-        if (c == TELIVA_BACKSPACE) {
+        if (c == KEY_BACKSPACE || c == DELETE || c == CTRL_H) {
             if (qlen != 0) query[--qlen] = '\0';
         } else if (c == ESC || c == ENTER) {
             editorSetStatusMessage("");
@@ -1095,7 +1097,9 @@ static void editorProcessKeypress(lua_State* L) {
     case CTRL_F:
         editorFind();
         break;
-    case TELIVA_BACKSPACE:
+    case KEY_BACKSPACE:
+    case DELETE:
+    case CTRL_H:
         editorDelChar();
         break;
     case KEY_NPAGE:

src/lua.c

@@ -451,8 +451,8 @@ static void recent_changes_menu (int cursor, int history_array_size) {
   draw_string_on_menu("older");
   /* draw_menu_item("↑/backspace", "newer"); */
   attroff(A_REVERSE);
-  mvaddstr(LINES-1, menu_column, " ↑/" TELIVA_BACKSPACE_KEY_NAME " ");
-  menu_column += (strlen(TELIVA_BACKSPACE_KEY_NAME) + 4);
+  mvaddstr(LINES-1, menu_column, " ↑/backspace/delete/^h ");
+  menu_column += 23;
   attron(A_REVERSE);
   draw_string_on_menu("newer");
   draw_menu_item("^e", "edit/add note");
@@ -616,7 +616,9 @@ void recent_changes_view (lua_State *L) {
         if (cursor > 1) --cursor;
         break;
       case KEY_UP:
-      case TELIVA_BACKSPACE:
+      case KEY_BACKSPACE:
+      case DELETE:
+      case CTRL_H:
         if (cursor < history_array_size) ++cursor;
         break;
       case CTRL_E:
@@ -649,6 +651,7 @@ static void big_picture_menu (void) {
   menu_column = 2;
   draw_menu_item("Esc", "go back");
   draw_menu_item("Enter", "submit");
+  draw_menu_item("^h", "back up cursor");
   draw_menu_item("^u", "clear");
   draw_menu_item("^r", "recent changes");
   attrset(A_NORMAL);
@@ -811,7 +814,7 @@ restart:
       mvaddch(LINES-2, x, ' ');
     mvprintw(LINES-2, 0, "Edit: %s", query);
     int c = getch();
-    if (c == TELIVA_BACKSPACE) {
+    if (c == KEY_BACKSPACE || c == DELETE || c == CTRL_H) {
       if (qlen != 0) query[--qlen] = '\0';
     } else if (c == ESC) {
       return;

src/teliva.h

@@ -11,11 +11,6 @@ enum KEY_ACTION {
   CTRL_F = 6,
   CTRL_G = 7,
   CTRL_H = 8,
-#if __APPLE__
-  TELIVA_BACKSPACE = 127,  /* delete */
-#else
-  TELIVA_BACKSPACE = KEY_BACKSPACE,
-#endif
   TAB = 9,
   ENTER = 10,
   CTRL_K = 11,
@@ -27,12 +22,7 @@ enum KEY_ACTION {
   CTRL_X = 24,
   ESC = 27,
   CTRL_SLASH = 31,
+  DELETE = 127,
 };
 
-#if __APPLE__
-  #define TELIVA_BACKSPACE_KEY_NAME "delete/backspace"
-#else
-  #define TELIVA_BACKSPACE_KEY_NAME "backspace"
-#endif
-
 #endif